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Thread: How a simple valve adjust can ruin your whole day.

  1. #1
    Rust Free'ish zKars's Avatar
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    Default How a simple valve adjust can ruin your whole day.

    Hi everybody! It's me, the "I can't believe I did that" guy.....

    Well, believe it or not, I have another "learning experience" to share. So grab a coffee and get comfy.

    Working on a new friend's 78z over the last few days, trying to get it ready for an "out of province inspection". Your Canucks will know what I mean. When moving a car to new province, everything has to work, and no rust holes or no insurance. Quite a challenge for most Z's, this one is no different.

    While doing a million other things, we decided to investigate a small engine "rattle" that happens under any amount of power "on" application. Not good. Bad bearing, slap happy piston, loose valve train? Letís find out.
    Started with a valve lash check and setting. Off comes the valve cover. Well, it came off but the gasket didn't so much, had to be scrapped off. Then there was some RTV stuff left over that was doing a great job of gasket sealing to peel off, and we all know how you don't want those little tendrils of that crap getting in the oil, so while I was peeling and digging it off, I stuffed a standard blue shop rag sheet in front of the timing gear to prevent RTV bits from going down there, cuz most of the RTV was on the front part.

    Finished the clean up and proceeded to start checking valve clearances. Right away I notice that #1 rocker is super loose. Have to jack up the adjuster about 6 feet (slight exaggeration) to get .010 clearance. Yeah, because the valve is stuck partly open, the spring pack is about 0.10 lower than its mate next to it. I can push it down and it pops back easy enough, but right to a nice stuck position. Alright, thereís the rattle source. Stuck/bent exhaust valve. Proceed to start spinning the engine with my remote start button and checking a few more looking for loosy gooseys .

    Just about then, the car's owner who's working with me tells me to hold it, that blue rag is caught up in the timing chain/gear. Sure enough, I'de left that thing down in the timing cover and it got dragged up and is now nicely distributed over the cam gear
    between it and the chain. We're talking a thin synthetic blue towellete here, we just grab its bits and spin the engine and get it clear. Its shredding into bits and pieces its so thin and weak. No biggy right? Read on....
    Finish setting the valves, which are all somewhere from spec to spec x 3 too wide, slap the cover back on with a new gasket and try to start the car. It cracks but we're getting no fire. Nothing. Ok, what did we do?

    First I had just yanked the plug wires off, didn't check what order they were in, they were just zip tied together, not in nice ordered clips, so who knows how the PO had left the timing or drive spindle. Could be anywhere. So set the engine to TDC
    and the dizzy is pointing to one, so just put them back on again in stock order and position. Still no go. Check spark, good, all cylinders. Check each injector with noid light. Flashing. Check fuel pressure. Good. oh oh...... What the hell have I done.

    Swap ECM's. Nope, same. Threw timing light on #1 and check while cranking. Yup, right at 15' ish, good enough. Hmmmm, spark, fuel, timing, what else do you need? Compression???? Pull the plugs and stick the comp gauge on #1. I know its going to be 0 with that bent valve. Sure enough. Then I check #2. Its 0 as well..... ?????? And 3..... and 4 ...... oh no...... and 5, and 6, all = 0.000000000 How is this possible?

    To make a long story short, hour and half later, heads on the bench, all 6 exhaust valves are bent. Yup, all six. Nice nick in each piston, nice shiny spot on each valve face. The timing chain slipped on the cam gear by about 5-6 teeth when that thin, feather weight, POS blue paper towel got in between there, causing a not too surprising detrimental effect on piston/valve clearance. When you think about the force required to stretch the chain to make that happen, I initially dismissed it as impossible. No way that piece of fluff did anything bad. Yeah, right.

    What I hadn't considered was the incredibly loose stretched timing chain on this old well worn L28..... I can *almost* slip a tooth by hand it's so loose with no tensioner pressure. Just took a little old piece of near-nothing to bunch up "just so" and make it happen. I'll bet you couldn't do that again if you tried on purpose all night long.

    I had actually noticed that the cam seemed out of time earlier but didn't catch on. When I was setting TDC to check timing and dizzy alignment after it didn't start, I was peering in the oil filler hole for #1 bunny ears, and noticed that the centerline of them wasn't at 12:00 at crank TDC, more like 10:00....

    So all you engine tinkerer's out there, beware! Even the slightest mis-step can lead to disaster without you even knowing you done it... Runs, set the valve, doesn't run. How do you get that wrong?
    Of course now Iím thinking about that initial stuck valve that I found before the engine turned with the rag in it. Just how did that happen? Maybe the chain had already slipped a couple of teeth before I got there due to that crazy loose chain, just enough to take out that one valve, and my rag trick just finished off the other 5 by slipping it a couple more.

    Letís just say thatís true and not ALL my fault.. Yeah, that feels better. A littleÖ.

    Well Itís a good thing I have all them old heads in the shed..... Eenie meenie minie moh...
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

    www.zKars.com
    www.calgaryzclub.ca
    Reference materials
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    That is the first verified account I've read of a chain actually jumping a tooth (or two). It gets proposed all the time but I've never seen it verified that it actually happened. Thanks for the story.

    You probably saved the owner the cost of new pistons from the slippage happening at high RPM. He owes you.
    1976 280Z, with some minor modifications

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    My last valve adjustment (actually just an inspection) I left fuel injector wires where they got pinched between the valve cover and the head. Took me weeks to figure out what the heck had gone wrong with the FI, in the meantime ordering lots of replacement parts.

    Like you say, a moment of carelessness can result in carless-ness.

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    Rust Free'ish zKars's Avatar
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    I agree. Chain tooth jumping was just a dirty rumor for me as well until now. Though it seems to take quite a combination of a loose chain and some "help" apparently.

    Thanks for the additional support to the "it ain't ALL my fault" threory as well....
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

    www.zKars.com
    www.calgaryzclub.ca
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  5. #5
    Jim Arnett jfa.series1's Avatar
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    Yet another example of "no good deed goes unpunished!"

    Jim Arnett
    HLS30-15320 12/1970, original owner
    L24-020208 (original)
    IZCC Original Owner Registry #53

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    Boat Anchor Repairman Captain Obvious's Avatar
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    I usually follow mine up with a resounding shout of "I did NOT just do that!!"

    That's a pretty good one, BTW!

    Quote Originally Posted by jfa.series1 View Post
    Yet another example of "no good deed goes unpunished!"
    Haha!! A philosophy that I quote often as well.

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    zKars

    Don't feel all that bad. I was helping my brother out before he went for a long trip in Northern Arizona (he drives a 620). I figured that it be nice to get him a new fan clutch as the old one was stuck on - as in it was on all the time. Well in 620's the waterpump and fan is one piece (yay) so new waterpump sweet. All was going great right until the end, when I tightened the one LONG bolt - you know the one that goes into the block. Took it about 1/16 of a turn to fast and CRACK! Snapped right off. Long story short, three front cover replacements his truck is in running shape.

    As for chains, I did mine a year after I got my car, as it had an annoying rattle - sounded like the chain (which is still there mind you). The old chain I took out was roughly 2" longer then they new one - and based on records I had my car sat for 5 years and didn't move. So its possible that your friend's chain stretched even more.

    Jan
    1976 280Z
    HLS30288273

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    Nova Scotia,Canada,Earth Blue's Avatar
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    dang that is a bummer Jim....good thing you were there to resolve it. I wonder if there are marks on the inside of the valve cover that indicates the loose chain?
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


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    Registered User siteunseen's Avatar
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    Quote Originally Posted by Blue View Post
    I wonder if there are marks on the inside of the valve cover that indicates the loose chain?
    I remember somebody's doing that, the tensioner or one of the side guides caused it, maybe Grant with the yellow '77?
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User siteunseen's Avatar
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    It was Hardway's valve cover.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Rust Free'ish zKars's Avatar
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    Wow that's hard to believe! Its scored all the way around!

    Its not clear just how close the chain must be to the cover until you see something like this.

    Does this mean it was loose enough to be "floating" off the teeth enough to be rubbing the cover over that much of its circumference? Hard to imagine how this looks running, but there's the proof.

    I haven't really looked under the cover of mine, other than to note how black and grundgy is looks.... I'll report back.
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

    www.zKars.com
    www.calgaryzclub.ca
    Reference materials
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    Registered User Hardway's Avatar
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    I will add to this since that is my valve cover picture. Blue and I did a valve adjustment on my car several weeks ago due to a slight rattle we heard. We kept the blue shop towels away and got everything in spec, now its as quiet as a sewing machine. My chain has no shortage of tension on it and I cannot hear it scraping or touching the valve cover when its running. Even used a mechanics stethoscope and all seemed fine.

    It is a very unfortunate series of events but it happens to all of us. Add to the fact all of our cars are 40+ years old, many with questionable past ownership and maintenance. All of this seems to magnify any failures we experience, weather they are created by us or by sheer wear and tear.
    08/1970 240z Series-1 #8011 - Silver, black int., 2.4L I-6, 5spd, 90% restored.
    06/1973 VW Karmann Ghia - Black convertible, 4spd, 1600cc air-cooled engine.
    11/2013 Scion FR-S - Silver, 6spd, a car with the soul of a Z for the modern times.
    Restoration thread of my old '72 240z -> http://www.classiczcars.com/forums/o...1972-240z.html

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    Rust Free'ish zKars's Avatar
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    Hardway, so from what your saying, it seems then that there was no actual touching of the chain to the valve cover. You can confirm that there is no marks in the aluminum?

    If thats the case, then the patterns we see are likely just "cleaning" of the previous dark varnish coating by oil spraying from the chain. Did you recently change to so some of that modern "detergent" oil?
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

    www.zKars.com
    www.calgaryzclub.ca
    Reference materials
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    Guys

    I have a bit of a theory I want to run by you. For what I remember the chain in tensioned by oil pressure using the tensioner. When you're turning your engine with a remote start I don't believe enough pressure builds up to actually put any "tension" on the chain. I say this because the last time I did a valve adjustment on my brother's 620 (L20) I noted that the backside of the chain - being the right hand side looking at the front of the motor - was rather loose and floppy. Its a new chain and I know I installed it correctly as I did it twice (see above post). Could that and the "blue shop towel of doom" caused the chain to skip a tooth or five while you were not paying attention.

    The other reason I bring this up as last time I started the Z in the winter and revved the motor too quickly - before oil pressure built - there was a nice chain rattle coming from my engine. The chain is new - installed about two years ago and I know I did this right as I took forever doing it - literally took me like 8 hours, took my sweet time.

    Thanks
    Jan
    1976 280Z
    HLS30288273

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    Nova Scotia,Canada,Earth Blue's Avatar
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    Quote Originally Posted by Pomorza View Post
    Guys

    the chain in tensioned by oil pressure using the tensioner. When you're turning your engine with a remote start I don't believe enough pressure builds up to actually put any "tension" on the chain.

    Thanks
    Jan

    Absolutely correct but there is one more detail: the chain should initially be installed with 0 slack. the tensioner simply maintains a firm pressure and takes up slop over time as the guides wear and the chain stretches.

    Here is the initial install with no slack:

    Last edited by Blue; 07-20-2013 at 07:14 AM.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


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    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


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    Registered User siteunseen's Avatar
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    Default Curiosity got me!

    I pulled the cover off my '77 that only has about 1500 miles on a newly rebuilt motor, also looked at the one I took off my 240 about a month ago. It has to be so close that the oil is slinging against the cover and making those footprints like Zkars says. I use VR1 and my valve cover didn't look like that when I put the motor together back in September '12.
    Sorry about that Hardway.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User darom's Avatar
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    zKars, don't feel too bad - you were helping your friend out. We are all human and make mistakes.

    It took me 2 days to figure out the no-start condition on my 76. When I replaced the intake's exhaust gasket, I stuffed paper towels to keep dirt out. After cleaning and putting the intake back, I couldn't figure out why even with the air/fuel/spark I couldn't start the damn thing. Of course, I had a bunch of paper inside the cyl. head! :-) It is funny now, but at that time I felt like hitting myself with the hammer on the head to teach a lesson to pay attention.
    - 1976 280Z
    - 1967 Camaro RS

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    Quote Originally Posted by Blue View Post
    Absolutely correct but there is one more detail: the chain should initially be installed with 0 slack. the tensioner simply maintains a firm pressure and takes up slop over time as the guides wear and the chain stretches.

    Here is the initial install with no slack:

    Blue

    I remember this fact also, but if someone was to install the chain improperly or due to age the chain had strecthed enough to not be at 0 slack couldn't be possible that enough slack was there that the motion of the remote start caused it to jump a tooth? It's just a thought.
    Jan
    Last edited by Pomorza; 07-20-2013 at 09:00 PM.
    1976 280Z
    HLS30288273

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    Rust Free'ish zKars's Avatar
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    More details now that I'm made some positive progress. The car is running and left for its new home last night. The original power-on ticking/clicking noise that caused the iniitial investigation is gone. Replace with much more satisfying and familiar cold clearance set valve train clatter.

    Blue/Jan, you guys are spot on about new chain being tight ie no slack. I installed the "new" (to him) head and a new chain and guide,s and as usual, the chain is a VERY tight fit.

    I got the chain on its correct clocking, then when re-installing the (curved) tensioner, I had to use a c clamp across the chainand guide in the center to lightly compress it to get the top bolt (slotted hole) in the tensioner. Same when re-installing the tensioner. Tight fit indeed.

    I took a picture of the old and new chain on the bench to show the length difference (sorry will post it later). The old is clearly stretched, but not quite to the extent I expected. The old head had shims under the towers as well which I removed for the near-stock thickness N42 that took its place (used his towers/cam/rockers/lashies). Would have been impossible to get that chain on with those shims in there.

    I looked at the valve cover and it looks exactly like the two shown above. Not a mark/gouge in the cover that I can feel with my nail or finger, just the cleaned paths made by fresh modern oil clearing away varnish.

    And in general, with more thought about what caused the tooth skip to start with, I'm more and more skeptical about the rag having anything to do with it. I just can't believe the texture and material strength (or lack of it) of it would be able to create a wad that would have had sufficient compressive strength to cause this. The rag was well distributed around the gear when I stopped dug it out. No concentration in one spot. I'm now inclined to believe its a combination of the herky/jerky motion of using the remote crank switch and the very loose chain with no tensioner pressure that ate my lunch. Beware!

    Another learning point to add to the conversation. When using the starter to rotate things, it's now very clear that it had no problem bending the valves as it rotated the engine without so much as a hiccup that might give you clue something bad was happening. At one point late in the process, (actually just before the realization of doom occured) I'de put a socket on the crank nut to move the engine to exact TDC to get things lined up for another timing check. The engine rotated smoothly then BANG, it stopped dead. When back the other way, smooth until, BANG, same thing. Dead stop. I put quite a bit of pull on the handle and couldn't budge it. So its clear that HAND rotation or maybe pushing the car in gear is the right technique, if you have ANY reason to suspect an old loose chain or you're working on a new motor and testing if you turns over. Sounds obvious now, doesn't it?
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

    www.zKars.com
    www.calgaryzclub.ca
    Reference materials
    www.xenonS30.com

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    Rust Free'ish zKars's Avatar
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ID:	64720and here are some pics
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

    www.zKars.com
    www.calgaryzclub.ca
    Reference materials
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    Rust Free'ish zKars's Avatar
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    Finally had a chance to remove the valves from the head.

    Enjoy the painfull art!

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    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

    www.zKars.com
    www.calgaryzclub.ca
    Reference materials
    www.xenonS30.com

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    No more body roll! SteveJ's Avatar
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    Ouch.
    73 240Z
    74 260Z

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    Registered User LeonV's Avatar
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    Quote Originally Posted by SteveJ View Post
    Ouch.
    Ouch is right!
    2/74 260Z

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    That's actually not as bad as I've seen. Still painful to look at but I've seen much worse.
    1976 280Z
    HLS30288273

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    Supporting Member 240dkw's Avatar
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    Jim: as we talked about yesterday here is a photo of the inside of the valve cover. I did not touch it with a rag or anything.
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    Registered User chaztg's Avatar
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    worst day in my own Z history was when I thought my car's "cam timing" was off and it turned out to be a separated harmonic balancer (outer grooved belt part was free spinning on the bolted-to-the-crank center part). Needless to point out, TDC wasn't TDC, and my "adjustments" didn't go too well. Looking back, I can't believe the lack of caution on my part to not catch the fault before it caused the inevitable you know what...My motor's valves were nowhere nearly as bad as those. I can still remember the godawful noise the motor made when I turned it over--kind of a tortured mechanical whooping sound.
    It always pays to double check your baseline settings. I learned an expensive lesson, but I have nice new stainless steel valves!

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